In the prior art, thermally expandable sheets in which a thermally expansive layer containing a thermally expandable material foaming and expanding according to the amount of heat absorbed is formed on one side of a base sheet are known. The thermally expansive layer can be distended in part or in whole by forming a photothermal conversion layer converting light to heat on the thermally expandable sheet and irradiating the photothermal conversion layer with light. Moreover, methods of forming a shaped object (stereoscopic image) having a stereoscopically uneven surface on the thermally expandable sheet by changing the shape of the photothermal conversion layer are also known (for example, see Patent Literature Unexamined Japanese Patent Application Kokai Publication Nos. S64-28660 and 2001-150812).
There is a problem in that some conventional thermally expandable sheets are yellowish and thus have a degree of whiteness that is low. In such a thermally expandable sheet, there is also a problem in that expressing bright colors is difficult when forming a stereoscopic image on the surface.
Therefore, there is a demand for a thermally expandable sheet comprising a surface that has an improved degree of whiteness.
The present disclosure is made with the view of the above situation and an objective of the disclosure is to provide a thermally expandable sheet comprising a surface that has an improved degree of whiteness and a method of producing the thermally expandable sheet.